The preparation of infused fruit products has conventionally been carried out by adding fresh fruit to a tank containing a warm concentrated sugar solution or sugar syrup, and then stirring the fruit and sugar syrup together. Due to the greater amount of dissolved solids in the bath versus that present in the fruit, osmotic exchange takes place resulting in the infusion of sugar solids into the cellular portions of the fruit. During osmosis, the syrup diffuses inwardly into the fruit while water contained within the fruit undergoing infusion diffuses outwardly through the cell walls of the fruit.
A principal disadvantage associated with conventional fruit infusion processes is that the high bath concentrations necessary to infuse the fruit to the desired solutes level often cause the fruit to shrivel.
Although the rate of infusion of bath solutes into the fruit approximates the rate of water loss, or exfusion, from the fruit early in the infusion process, at later times the loss of water from the fruit continues at close to its initial rate while the influx of solutes into the fruit proceeds much more slowly. This loss of water from the fruit becomes more pronounced as the bath solutes concentration is increased, and is responsible for the undesirable shrinkage observed when highly concentrated infusion baths are employed.
Shrinkage could theoretically be reduced by use of a lower-concentration infusion bath, but infusion rates decrease with decreasing bath concentration. Also, the achievement of the desired solutes level in the fruit is further impeded by the concomitant dilution of the infusion bath by the fruit water, which unacceptably slows the infusion rate.
Shrinkage can be reduced by the use of a series of baths of gradually increasing concentration, but this approach is also slow and may present mechanical difficulties. However, due to the necessity to avoid osmotic shock, typical fruit infusion processes employ infusion times of 10 days to 2 weeks.
It is, therefore, an object of the present invention to provide a process for fruit infusion which allows a balance to be maintained between fruit water loss (dehydration) and bath solutes infusion so that the fruit solutes may be raised to the desired level before detrimental shrinkage due to dehydration occurs.
It is another object of the present invention to economically decrease the time required to achieve the desired dehydration infusion of fruit.
It is another object of the present invention to provide a process for fruit infusion wherein the fruit is infused to about the 32 to 58% solids level, and a water activity level of about 0.96 to 0.82, preferably 0.96-0.85.